This application claims the priority of German Patent Document No. 197 25 009.2, filed Jun. 13, 1997, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method for the treatment of a methanol reforming catalyst. Such catalysts are known in various compositions. See, for example, patent applications DE 35 31 757 A1 and EP 0 201 070 A1. Usually the catalyst material is placed in the form of a charge of catalyst pellets into the reforming reaction chamber of a methanol reforming reactor. Such reactors serve, for example, for the production of hydrogen for the fuel cells of a fuel-cell-operated motor vehicle by the hydrogen reforming of liquid methanol carried by it.
Various methods have been proposed for sustaining a high catalytic activity and for the achievement of a long life of the methanol reforming catalyst. Thus, in patent application JP 4-141234 (A) a special formulation of different metal oxides is given for obtaining a catalyst with a long life and high activity and selectivity.
In patent application JP 63-310703 (A) the catalyst material is subjected in the reforming reaction chamber of a methanol reforming reactor to a reduction reaction prior to the start of the operation of the reforming reaction, leading to a reduction of the volume of the catalyst. A compression spring-loaded, movable cover plate keeps the catalyst material that has been placed in the reaction chamber in the form of a charge of pellets compressed in a tight pack. The reduction reaction is a process necessary for the operation of a copper catalyst. The shrinkage that occurs is definitely less than the shrinkage that occurs during the normal reforming operation.
In patent application JP 63-315501 (A) it is proposed to place an air chamber between a burner and a reforming reaction chamber, through which air can be fed in a controlled manner in order to keep the catalyst temperature at a given level.
In a process disclosed in patent application DE 33 14 131 A1, to prolong the life of the methanol reforming catalyst, the methanol is freed of any chlorine compounds contained therein, before it is brought into contact with the catalyst.
In patent application GB 2 132 108 A it is known, in starting up a methanol reforming reactor to heat the catalyst material present in the reaction chamber rapidly by burning methanol with a stoichiometric or less than stoichiometric oxygen content and passing the combustion exhaust gases both through a tempering chamber in thermal contact with the reaction chamber and also through the reaction chamber itself. Water can be sprayed into the combustion gas stream that is fed into the reaction chamber in order to prevent overheating. As soon as the desired reforming temperature is reached the heating process is terminated and the reforming process is started. This is the case typically within less than a minute.
In patent application DE 1 246 688 a methanol reforming reactor is disclosed that contains a nickel catalyst and a zinc-copper catalyst. In use, the reforming reaction is periodically interrupted for catalyst treatment phases which comprise a regenerating phase and optionally a subsequent nickel catalyst reactivation phase. In the regenerating phases the reactor is flushed out with a gas containing free oxygen at a temperature between 150.degree. C. and 450.degree. C., while in the nickel catalyst reactivation phases a purging is performed with a gas containing free hydrogen. The manufacturing process for the nickel catalyst prior to its use in the methanol reformation includes at the end a treatment of a nickel foreproduct in a reducing atmosphere for reduction to metallic nickel for several hours at temperatures between 150.degree. C. and 600.degree. C. For the zinc-copper catalyst, at the end of the process by which it was made, provision can be made for heat treatment at 250.degree. C. for four hours to remove any granulating aid that may have been used.
A known fact of virtually all current methanol reforming catalysts is that in the first hours of the operation of methanol reforming they undergo a marked loss of volume that results in a corresponding lessening of the performance of a methanol reforming reactor containing the catalyst.
The present invention is addressed to the technical problem of devising a method for treating a methanol reforming catalyst such that, in the first hours of operation, a methanol reforming reactor containing the catalyst will exhibit no marked loss of performance caused by any lessening of specific catalytic activity due to the catalyst's loss of volume.